Linyphia triangularis grows up to long. The carapace is pale brown with darker markings along the edges and down the centre line; the opisthosoma has a coarsely serrate brown band against a white background, with further brown markings along the sides. The legs are greyish brown, and bear many long spines.
Linyphia triangularis lives in a wide range of habitats, where it may be found among low bushes and vegetation. It spins a horizontal sheet-web, and rests on the underside of the web for its prey. Adults are active in the late summer and autumn. The prey are snared by "barrage lines" above the web, and fall onto the horizontal sheet, where they are killed by L. triangularis, but are not wrapped in silk.